exchemist

I suppose you could look at that way. But that's still a bit theoretical, compared to the width of a spectral line. Is there not some classic experiment that shows how increasing precision in position leads to lower precision in momentum (i.e. a broader frequency distribution, or something? How about limitations on focusing a laser beam to a point, or something like that?

Indeed. However the OP seems to be asking for practical examples in which position/momentum uncertainty is experimentally apparent. I can't think of one offhand. Can you? There are classic examples of the related energy/lifetime uncertainty in things such as the width of spectral lines (uncertainty broadening), but position/momentum? Hmm.

Markus, this has taught me several things I did not know. As usual, when you post....😃

There's nothing magic about using 1 molar solution. Sure, 0.5 M would need half the mass in the same volume of solvent. But as far as strength of the acidity goes, if you are using a weak acid the actual acidity of the solution you make, i.e. the concentration of H+, will not be linear with concentration of the acid you add, since dissociation is only partial. It will take place to a greater degree, as a proportion of the acid added, in a more dilute solution, because the equilibrium HA <-> A⁻ + H⁺ will lie further to the right at low concentrations of H⁺ and A⁻ .

You can get inflammation in your larnyx, pharynx etc. with colds, as these viruses make the circuit of one's respiratory mucous membranes, so it could just be that. I have not heard of anything specific to covid of that nature. I expect it will go away. But it's a funny virus so you are wise to stay alert.

Could that be due to a difference in convention?

Yes I mole weighs 192g, so 192g dissolved in 1litre would be a 1 mol solution. So for 250ml you need a quarter of the amount. Not sure where your 1/2 comes in - typo? (250ml is 1/4 of a litre of course, as you correctly imply in your calculation.)

I think you can get drain cleaner which is based on strong acids (some is also based on strong alkali), but I hesitate to suggest you try, as they are fairly nasty if you spill them on you - or anything else. Citric acid has a first pKa of 3.1 whereas acetic acid has a pKa of 4.76, so citric acid is a bit stronger but not much. (For comparison a strong acid such as HCl has a pKa of -6, so in a different ballpark entirely).

I used the term Ac a bit wrongly actually. Ac, strictly denotes the acetyl group, which is CH3CO - so I should have said Mg(OAc)₂. I'm retired and very out of practice, I'm afraid. Probably best to refer to it as Mg (CH3COO)₂ , to avoid getting into a nomenclature minefield. Regarding Zn's apparent low reactivity, acetic acid is a weak acid. At molar concentration (similar to vinegar), only about 0.4% is dissociated into H+ and acetate. If you had a molar strong acid, e.g. HCl, the reaction would be more obvious I think.

Electrons in atoms can be thought of as standing waves corresponding to resonant frequencies, ie. a series of harmonics. In fact the shapes of atomic orbitals are spherical harmonics, akin to the modes of vibration of a rubber ball if you hit it and look at how it vibrates with a strobe light. Each electron occupies a different quantum state. It has to, as electrons are fermions. "Shells" are simply groupings of related, but different states that are possible for an electron to occupy in an atom. Each shell comprises all the states that have the same principal quantum number, n. But n is only one of 4 quantum numbers needed to specify individual possible states. They others are: - l, which denotes the angular momentum and determines which subshell the electron is in (i.e. s, p, d, f etc), - m(l), which determines which member of the sets of s, p,d, f orbitals the electron is in (e.g p(z), d(x²-y²), etc), - and finally m(s) which determines the spin orientation within that orbital. So one can have a maximum of 2 electrons per orbital, one with spin orientation "up" and the other "down". In chemistry, this accounts for the pattern of the Periodic Table of the elements, each row corresponding to the highest occupied principal shell that is occupied, 1st row n=1 2nd row n=2 etc. (cf. Aufbau Principle.)

10 years is the general practice in the UK, certainly, though it is not recommended that everyone needs it. I used to get it topped up when I travelled abroad with Shell, as it was company policy, but not any more. If I worked with horses, or as a gardener, that would be different.

So, answering the actual, actual question😃, since MW of CaCO3 is 40+12 + (16x3) = 100, 2g would absorb 2/100 x 177.8 = 3.556kJ, wouldn't it?

Get yourself topped up with a booster. You'll have to wait a bit, seeing as you've just been infected, but keeping your booster immunisations up to date as per medical advice is by far the best thing you can do. Even then you can still expect to get covid from time to time, but far less badly unless you have some underlying condition. There is no need for anything to deal with the infection you have now, so long as symptoms remain mild. But from my own experience (I caught the original version before any vaccines were available, and lost my sense of taste and smell for several weeks) I would advise being careful how quickly you return to full normal activities, as it can leave you fatigued for a few weeks. Do not attempt to fight through any fatigue you may experience or it will slow down your recovery.

Hmm. I suspect that will be to do with the tendency of amino acids to exist as zwitterions. I don't think you can rely on an acid/base colour indicator to work, because of the basicity of the amine end. So you would have to find reactions that bind carboxylate specifically and thereby produce a colour change. Perhaps something involving a transition metal ion, for which RCOO- could be a coordination ligand?

Ah yes, probably. Let's see if our poster can take part in a conversation about this.

What reaction are you talking about?

OK have fun. Try it with zinc too - I'm a bit surprised you saw no reaction. By the way, I should have said Mg(Ac)₂ of course.

You might want to brush up on the Electrochemical Series. That tells you which metals are expected to react with acids to liberate hydrogen (basically anything with an electrode potential that is -ve relative to hydrogen, which is set at zero by convention.) An example here: https://chemguide.co.uk/physical/redoxeqia/ecs.html According to this, Mg is expected to react, and Cu is not. Zn however is slightly -ve, so would be expected to react, but not as vigorously as Mg. But there may be a protective oxide layer that interferes - I can't remember. The reaction product with Mg should indeed be MgAc. If the Mg strip has an oxide layer, I should think rubbing with wire wool (i.e. a scouring pad without soap impregnation) would be one way to get that off. Other, less ancient, chemists may be able to add to this or correct it......

I think this will just add confusion for our questioner, quite honestly. We have not been talking about the double slit experiment but about light reaching us from stars. All the stuff about the principle of least time etc. notwithstanding, nothing about the current QM model suggests that light quanta do not travel, for all practical purposes, in a specific direction, nor that their associated waves do not have a direction of propagation, even if it is only, strictly, a predominant one. The idea our questioner has, that a single photon has a wave that spreads out uniformly in all directions, is not correct and we need to make that clear, I think.

There is one big misunderstanding here, which is to think each photon spreads out in all directions. It doesn’t. An individual photon is emitted in a particular direction. So the issue of something behind the emitter absorbing the wave before it gets to you does not arise.

According to my (limited) understanding of Rovelli's relational interpretation, the wave function applicable from the cat's perspective is different from the wave function applicable from our perspective, so long as the box remains closed. There is not necessarily a single, absolute, wave function describing a quantum system: it depends on the informational state to which it relates. The cat, being inside the box , is in a different informational state from those outside and so a different wave function applies, from its perspective.

By being out of phase. Nothing to do with charge. What nonsense. The same wave (i.e. a single excitation) passing though 2 slits will form an interference pattern on the far side. This is basic.

Er, well, mastodons, sabre-toothed tigers, etc. appeared about 40m or more years later, from the Miocene onwards. The mammals that existed at the end of the Cretaceous were indeed small and shrew-like.

I have no experience with boiling chestnuts, as I usually grill them in their shells. I know that some things intrinsically tend to cook more evenly than others, though. Jerusalem artichokes (topinambours in French, aardpeeren in Dutch) are a bastard, some being still hard by the time others are disintegrating. Maybe chestnuts are like that. I suspect a (continental) cookery website will be the best place for advice.

You are attributing to me something said by @Airbrush